Printing telegraph exchange system



Wet. 31, 1933; F. s. HALLDEN 4 PRINTING TELEGRAPH EXCHANGE SYSTEM FiledNov. 5, 1931 2 Sheets-Sheet 1 INVENTOR FREDERICK G. HALLDEN BY 1% ATTOREY .Oct. 3l,'193 F. G. I-IALLDEN PRINTING TELEGRAPH EXCHANGE SYSTEM Fild N V- 1931 2 Sheets-Sheet 2 I I I l l I I l l I I I I I I I l I l l l lI l l l l l I I I I l l I l .IIIIIIIIhm:IIIIIIIIIIIII IHI" III-

| l l l I|I||||l| ||ll IIIIIIIIIIIIIIIIIIII lllllllll r I I I I I I I II I l I I I I I I I I I I I I l I I I I I I I I I I N E D L M G K m R ED E R F Patented Oct. 31, 1933 1,932,933 PRINTING TELEGRAPH EXCHANGESYSTEM Frederick G. Hallden, Bellerose, N. Y., assignmto InternationalCommunications Laboratories, Inc., Newark, N. J., a corporation of NewYork Application November 6, 1931. Serial No. 573,323

10 Claim.

This invention relates generally to step-bystep switches, and moreparticularly relates to step-by-step switches that can be employedinterchangeably asline finders or as connectors.

In automatic printing telegraph exchange systerns that provide automaticswitches for interconnecting any one of a plurality of subscribersstations with an operators position at a central station, it isfrequently desirable to equip each operators position for both sendingand receiving. With the ordinary type of stepby-step switches this canbe done only by associating with each operators position both a linefinder and a connector switch.

The object of the present invention is to eliminate one of these twoswitches by providing a step-by-step switch that can be usedinterchangeably as a line finder or as a connector.

Another object is to provide a switch of such construction that it canreadily be grouped with other similar switches in a manner well-known inthe art, for the purpose of increasing the efiiciency of each of theswitches in the group.

According to this invention, a plurality of subscribers stations and theoperators positions at a central station are associated through a groupof combination line finder-connector switches, each switch beingindividual to an operators position for outward service. A sequenceswitch pre-selects an idle switch in the group to answer the next callfrom a subscribers station. When a call occurs an interrupter, common tothe group of switches, is caused to step the selected switch until thecalling line is found. The subscribers line is thereupon connectedthrough the operated switch to the associated operators set, theinterrupter is dis-associated from the switch, and the sequence switchprepares the next idle switch to answer a subsequent call.

When a combination switch is used as a connector it is directivelycontrolled by an associated operators set, in the usual manner, toestablish connection to one of the subscribers stations.

Means are provided, while a combination switch is in use as a linefinder, for making it busy to the associated operators set, and while itis in use as a connector, for making it busy to the subscribersstations.

Referring now to the drawings, in which Fig. 1 should be placed aboveFig. 2 to show the arrangement of the elements of the system, Fig. 1discloses a subscribers station W, a combination line finder-connectorswitch X; and Fig. 2

discloses a sequence switch Y, and an operators set Z at a centralstation. It is to be understood that in actual practice a number ofsubscribers stations (but not more than 100) would be multiplied to thebank terminals of the switch X, and to the terminal banks of othersimilar switches (not shown) to permit connection between any one of thesubscribers stations and any one of the operators sets, such as at thecentral station. The sequence switch Y is shown as a ten point switch,but it is to be understood, that it may be provided with a number ofcontacts sufficient to provide connection to any desired number ofoperators sets.

The apparatus at the subscribers station W and the central operator'sset Z are similar to the apparatus disclosed in U. S. Letters Patent No.1,895,112, granted toG. S. Vernam. The line wire 1 from the subscribersstation W terminates at the central oflice in a line relay 2. The linerelays are divided into groups, there being ten groups to each onehundred lines. A group relay'3 (Fig. 2) is common to each group of tenline relays, so that when any line relay is energized, the group relayassociated with it is also energized. The group relay, 'when operated,marks, or renders selectable, the level contact of the verticalcommutator 8 in a predetermined idle combination switch, while the linerelay, when operated, marks the individual test contact 20 in thatswitch. The sequence switch Y, which is common to the combinationswitches, is caused to rotate whenever a combination switch has found acalling line. In rotating sequence switch Y picks out an idlecombination switch, such as X, thus conditioning that switch to answerthe next call from the group of one hundred subscribers lines. On theshaft (not shown) of the switch X are mounted a private wiper 4, a linewiper 5, and a test wiper 6. These wipers move over contacts in theprivate line and test banks respectively of switch X when that switchrotates. Also mounted on the same shaft (not shown) is a vertical wiper'7 which moves over the contacts in the vertical commutator 8 of theswitch X when that switch is stepped vertically. Upon the operation ofthe group relay, assuming that combination switch X has previouslybeenselected by sequence switch Y, switch X first steps vertically topick out the group of calling lines, and then rotates horizontally untilthe calling line is found. When the switch X is first operated a guardlamp is operated at the operators set Z.

llO

When the calling line is found this line is made busy at each of theother combination switches, the current in this line is reversed thuscausing the subscriber's printer motor to be started and the current inthe line circuit increased to its signalling value. Telegraphiccommunication can then be carried on between the calling subscriber Wand the operators set Z. At the same time the sequence switch Y isoperated to associate another idle combination switch with the group of100'subscribers lines. When communication has ended, the central stationoperator releases the combination switch X and dis-establishes theconnection.

When the combination switch X is employed as a connector, inestablishing a connection between a central station set Z and thesubscribers station W, the key 9 is operated to connect the dial 10 tothe dial lead 11 and to the slowrelease relay 12. This relay thereuponenergizes grounding the contact corresponding to switch X on the lowerbank of sequence switch Y, thus making switch X busy and preventing itsseizure by a calling line. The switch X is then operated by dialimpulses, in the usual manner, to establish connection with subscribersstation W. When connection is established the operator at Z reverses thecurrent over the subscriber's line 1, starting the printer motors at thesubscriber's station W. As the operator's printer motor (not shown) isrunning continuously, telegraphic communication can then be carried on.mentioned above, is under the control of the central station operator.

The detailed operation of the system is as follows: to make an inwardcall the subscriber at W operates the key 13 to shunt-the lower or highresistance winding of the line relay 14. The removal of this highresistance from the line circuit causes the line current to increase toa value which operates the line relay 2 at the associated centralstation over a circuit from grounded negative battery, winding of linerelay 2, contact B of the cut-off relay 15, equalizing resistance, upperwinding of polar line relay 14, contact of calling key 13, transmitter16, printer magnets 17, break key 18, and to ground. As polar relay 14is wound so as to close its contact only in response to positivecurrent, the circuit of motor control relay 19 remains open. Theoperation of line relay 2 completes at its A contact an obvious circuitfor operating the associated group relay'3, and at its B contactconnects ground to the test bank contact, corresponding to the callingline, in each of the combination switches, such as contact 20 of switchX. The group relay 3 is multiplied by conductor 51 to contacts A ofother line relays associated with the subscribers lines to which grouprelay 3 is common.

Assuming now that the sequence switch Y has previously been operated toprepare combination switch X to answer the next call, the operation ofgroup relay 3 completes two circuits for controlling the extent of thevertical and horizontal movements of switch X, and another circuit foreffecting the movement of that switch into engagement with the callingline 1. At its A contact, group relay 3 completes a circuit fordetermining the extent of vertical movement of all of its associatedswitches, such asX, though, of course, only the switch X, selected bythe sequence switch Y, will be operated. The circuit to switch X may betraced from negative bat- The release of the connection, as.

tery, winding of interrupter control relay 21, contact A of relay 3, tothe segment of the vertical commutator 8 corresponding to the level inwhich the contacts of the calling line appear. Similarly, negativebattery is extended to a corresponding segment in the verticalcommutator bank of each of the other associated switches (not shown)over conductor 50. At its B contact, relay 3 extends a parallel circuit,including the above-mentioned battery and winding of relay 21, through acontact in the upper bank of sequence switch Y to the test wiper 6,which co-operates with the test bank of switch X. Relay 3 also extends acircuit controlled by the interrupter 22, from ground, through theinterrupter contacts, contact C of relay 3, a contact on the middle bankof sequence switch Y, contact B of relay 23 of switch X, upper and lowerwindings of relay 24 of switch X in series, to grounded negativebattery. Conductors 49 extend to the B and C contacts of otherassociated group relays, so that any of such relays can upon operationcomplete circuits similar to the two circuits last traced. Theinterrupter pulses, which are of approximately dial frequency, thencause the contacts of relay 24 to-vibrate. The first closure of contactB of relay 24 causes slow-release relay 25 to energize over an obviouscircuit. The first succeeding closure of contact 0 of relay 24 causesvertical magnet 26 to energize over a circuit from grounded battery,winding of vertical magnet 26, winding of slow-release relay 27, contactB of off-normal contacts, contact 0 of relay 25, contact C of relay 24to ground. The switch X then takes one vertical step, thus openingcontact B and closing contacts A and C of the cit-normal contacts 42,thereby extending the circuit of vertical magnet 26 through contact A ofthe off-normal contacts and contact B of slow-release relay 27. Relay2'? and relay 25 remain operated when energized by pulses of dialfrequency.

At the time that relay 2'7 was operated, switching relay 28 at theoperators set Z was operated over a circuit extending from groundedbattery, winding of relay 28, contact A of key 9, contact A of relay 24,contact A of relay 27 to ground, and the circuit of the guard lamp 29was completed from grounded battery, guard lamp 29, and through contactA of key 9 over the remainder of the circuit above traced. Guard lamp 29lights informing the operator that switch X has been seized. Theswitching relay 28 connects ground on release key 30 through contact Eof the switching relay to release trunk 44, thus preparing a circuit forpreventing the switch from releasing after the calling line has beenfound. The switching relay 28 also locks through its F contact to groundon the release key 30. The switching relay 28 at its B contact alsoconnects the line circuit 31, through the winding of polar relay 32,transmitter 40, resistance and positive battery to ground.

Succeeding pulses from the interrupter 22 step the switch X verticallyby operating the vertical magnet 26. As the switch steps vertically theprivate wiper 4, the line wiper 5, and the test wiper 6, are broughtinto alignment with successive levels on their banks and the verticalwiper 7 is carried over the contacts of on the segment corresponding tothe operated group relay 3. When the vertical wiper 7 reaches thissegment the circuit of relay 21, previously traced to this segment, isextended through the vertical wiper I, contact D of relay 2'7, contact Cof operator's key 9 to ground. At the same time, private wiper 4, linewiper 5, and test wiper 6 are brought into alignment with the level oftheir respective contact banks in which the calling lirre contactsappear. Relay 21 then operates, shunting the interrupter contacts, thusholding relay 24 operated.

The pulsing circuit through the windings of relay 27 and the verticalmagnet 26, being now open at contact C of relay 24, the vertical magnet26 releases, and after an interval relay 27 also releases. The releaseof relay 2'? extends the pulsing circuit in parallel to the rotarymagnet 33 and the slow-release relay 34. The release of relay 27 alsoopens at its D contact the circuit of relay 21, whereupon this relayreleases, opening the shunt around the interrupter contacts. Relay 24again responds to the interrupter pulses, which are now efiective torotate the shaft (not shown) of the switch X. As the private wiper 4,the line wiper 5, and the test wiper 6 have been previously brought intoalignment with the level of their respective contact banks in which thecalling line contacts appear, the rotation of the shaft of switch Y,moves the several wipers over the contacts in the same level of theirrespective contact banks. On each level there are ten contacts, eachcorresponding to a subscribers line, and the several wipers are adaptedto move over the ten contacts on the same level in their respectivebanks. In the present case, depending upon the position of the contactscorrespondingto station A on the level, the switch wipers will besuccessively stepped until they come into contact with the bank contactscorresponding to the calling line.

When these bank terminals are reached a circuit is closed for operatingrelay 21, which circuit may be traced from battery, through the windingof relay 21, contact B of relay 3, contact of upper bank of sequenceswitch Y, test wiper 6, test bank contact 20 to ground on contact B ofline relay 2. Relay 21 then operates, again shunting the interruptercontacts to hold relay 24 operated. The switch X is thus brought intoassociation with the contacts of the calling line. During the rotaryseries of impulses, relay 34 is held operated. A short interval afterthe end of this series of pulses, relay 34 releases. A circuit isthereupon closed for operating outoff relay 15 and relay 23 in series.This circuit may be traced from grounded battery, winding of cut-ofirelay 15, private wiper 4 of switch X, contact B of relay 34, lowerwinding of relay 23, contact B of relay 35, contact A of relay 25, andto ground. The operation of relay 15 disconnects the subscribers line 1from the line relay 2 and connects it to the line bank contact of switchX. The line relay 2 thereupon releases. The release of line relay 2removes ground from group relay 3 and from relay 21, releasing theserelays. This dis-associates the interrupter'circuit from the group ofswitches associated with sequence switch Y. Only contact F of relay 23,which is nearest to the core, is closed by the energization of the lowerwinding of that relay, but the closure of contact F completes a lockingcircuit from battery, upper winding of relay 23, contact F, contact B ofrelay 25 to ground. Relay 23 then completely operates. Contacts H and I,in opening, break the circuits of the rotary magnet 33 and the releasemagnet 36 respectively. The closure of contact G of relay 23 extends theline circuit 1 through contact B of switching relay 28. winding of relay32, transmitter 40, to grounded positive battery. The closure of contactE of relay 23 connects ground to the cut-off relay 15, holding thatrelay operated, and connects ground to conductor 37, multipled to theprivate bank contacts corresponding to the calling line, in each of theother combination switches, thus, in a manner to be described later,making the calling line busy to calls from the central omce. The closureof make-before-break contacts 0 of re lay 23 transfers the windingcircuit of relay 24 from the interrupter controlled ground, to ground onthe release trunk 44 from release key 30.

The closure of contact A of relay 23 completes a circuit for operatinggreatly 38 of sequence switch Y which may be traced from groundedbattery, winding of relay 38, contact of stepping magnet 39, contact ofthe lower bank of the sequence switch Y to ground on contact A of relay23. Relay 38 then operates, connecting ground to the stepping magnet 39.Energization of the stepping magnet 39 opens the circuit to relay 38,and the release of this relay in turn effects the release of thestepping magnet 39. The release of stepping magnet 39 causes the wipersof sequence switch Y to advance one step. This reciprocal action betweenthe relay 38 and the stepping magnet 39 causes the sequence switch Y tostep from one terminal to the next until a terminal is reached which isassociated with an idle line finderconnector switch. When the sequenceswitch Y has stepped to such a position, the circuit through the lowestwiper of the sequence switch is no longer grounded, that is, it isgrounded neither at contact A of a relay, such as 23, in the idlecombination switch selected nor at contacts of the slow-release relayl2. Relay 38 thus remains released, at this position of the sequenceswitch, and its release prevents the reenergization of the steppingmagnet 39. The combination switch now in connection with the sequenceswitch Y is thus conditioned to answer the next call from the group ofone hundred subscribers stations.

When the calling subscribers line 1 was extended to positive batterythrough relay 32, the current was reversed in the subscribers linecircuit 1. In response to this current reversal, the polar line relay 14at the subscribers station W operates, effecting the operation of motorcontrol relay 19. The operation of this last mentioned relay starts thesubscribers printer motor 41, and shunts the lower or high resistancewinding of the line relay 14. Calling key 13 should be released when themotor starts. Up to the time the line 1 was extended through the windingof relay 32 by the operation of switching relay 28, relay 32 wasincluded in a local circuit to ground to keep the circuit of the printermagnets 42 closed. The line circuit is now completed from groundedpositive battery, transmitter 40, winding of relay 32, contact B ofswitching relay 28, contact G of relay 23, line wiper 5, contact A ofcut-off relay 15, upper winding of line relay 14 at station W, contactof motor control relay 19, transmitter 16, printer magnets 17, break key18 to ground.

As the printer motor (not shown) at the central station set Z is runningcontinuously, telegraphic communication can now be carried on betweenthe subscribers station W and the central ofiice operators set. Afterthe message has been transmitted, the central ofllce' operator releasesby operating the release key 30, thus removing ground from the windingof switching relay 28 and from the release trunk 44. Switching relay 28thereupon releases, extinguishing the guard lamp 29, and applyingnegative battery through contact E of key 9 and contact C of relay 28 tothe line circuit 31. The removal of ground from the release trunk 44releases relay 24 of switch X. Release of relay 24 deenergizes relay 25,which in turn opens both windings of relay 23. Relay 23 releases and atits A contact removes ground from the contact on the lower bank of thesequence switch C; at its make-before-break contacts C disconnects relay24 from the release trunk 44; at its E contact opens the circuit ofcut-off relay 15 and removes ground from conductor 37, at its G contactdisconnects the line extending to operators set Z from the line wiper 5;at its I contact closes the circuit of the release magnet 36 fromgrounded battery, winding of the release magnet 36, contact I,off-normal contact C, contact D of relay 25, contact C of relay 24 toground. The release magnet 36 operates, restoring switch X to normal.The release of the cutoff relay l5 reconnects the subscribers line 1,through the line relay 2 to negative battery while the removal of groundfrom conductor 37 removes the busy condition from the private contactsof station W in the other switches.

The reversal of current on the subscribers line 1, cause polar linerelay 14 to de-energize motor control relay 19. The release of the motorcontrol relay stops the subscribers printer motor and cuts the lower andhigh resistance winding of relay 14 into the line circuit. All circuitsare thus restored to normal, and the next idle combination switch isconditioned, by sequence switch Y, to answer the next call from a groupof 100 subscribers lines.

To make an outward call, the central station operator, at Z, throws thedial key 9 to the centre position (note that this key is shown operatedto the right), thus establishing a circuit for operating slow-releaserelay 12, and for intermittently operating relay 24 of switch X by meansof dial 10. This circuit may be traced from grounded battery, bothwindings of relay 24 in series, winding of relay 12, dial lead 11, busylamp 45, contact D of switching relay 28, contacts of dial 10, contact Bof key 9 to ground. Relay 12 operates, grounding the contactcorresponding to combination switch X in .the lower bank of sequenceswitch Y, thus preventing a calling line from interfering with thatswitch and stepping the sequence switch, as previously described, untilits wipers engage the contacts of the next idle combination switch.Relay 24 also operates, closing an obvious circuit for slow-releaserelay 25. Relay 25 prepares a pulsing circuit for the vertical magnet35, which circuit, when completed, extends from battery, winding ofvertical magnet 26, winding of relay 27, contact B of off-normalcontacts 42, contact C of relay 25, to grounded contact C of relay 24.After the first vertical movement of the switch the pulsing circuit istransferred through contact B of relay 27, and contact A of theoff-normal contacts 42.

The operator now dials the first digit of 2.

two digit number corresponding to the bank position assigned to thecontacts of station W. Operation of the dial 1D alternately opensandcloses the circuit of relay 24, vibrating the tongue of that relay, thusintermittently opening and closing the previously traced pulsingcircuit.

The switch X is thus stepped vertically so that the wipers are inalignment with a level of their respective banks corresponding to thedialled digit. At the right end of the first series of dial pulses,relay 27 releases, extending the pulsing circuit in parallel to therotary magnet 33 and to the relay 34.

The operator now dials the second digit, and the resulting series ofimpulses again causes the pulsing circuit to intermittently open andclose, upon which the rotary magnet 33 causes the wipers 4, 5 and 6 tobe stepped around a corresponding number of steps. During the steppingof the wipers slow-release relay 34 remains energized, de-energizingonly after the wipers have come to rest on the selected bank terminals,and an opportunity has been given to test the condition of the calledline.

If subscribers station W is busy, the private bank terminal of the lineis grounded over conductor 37 (in a manner previously described) andconsequently relay 35 is operated over a circuit extending from thegrounded bank terminal, wiper 4, contact C of relay 34, contact D ofrelay 23, winding of relay 35 to battery. Relay 35 operates over thiscircuit, and when relay 34 releases, remains looked over a circuit frombattery, Winding of relay 35, contact D of relay 23, make-before-breakcontact E of relay 34, contact C of relay 35, to grounded contact A ofrelay 25. Operation of relay 35 at its D contact opens the pulsingcircuit, previously traced, preventing further operation of the rotarymagnet 33. Relay 35 at its A contacts also shortcircuits the upper orhigh resistance winding of relay 24, thus increasing the current in thedial lead 11, thereby lighting the busy lamp 45, informing the callingoperator that the called line is busy.

Upon noticing the lighted busy lamp 45, the operator throws the key 9to'the right to release the switch X. When the key is thrown to theright, ground is removed from contact B of the key and connected tocontact C. This extinguishes the busy lamp 45, and releases relays 12and 24. The release of relay l2 removes ground from the terminalcorresponding to switch X in the lower bank of sequence switch Y, sothat switch X is then free to answer a subsequent call.

The release of relay 24 opens the circuit of relay 25, and after aninterval the latter relay releases completing a circuit 'for the releasemagnet 36, which circuit may be traced, from battery, winding of releasemagnet 36, contact I of relay 23, oil-normal contact C, contact D ofrelay 25, to grounded contact C of relay 24. The release magnet 36 thenoperates to restore the switch X to normal. Upon releasing, relay 25 atits A contacts, opens the circuit of relay 35, which thereupon releases.Switch X and all associated relays are now restored to normal. At somelater time the operator may again try to establish connection with thecalled line.

If the called line had been idle, the private bank terminalcorresponding to this line would not be grounded. In this case, relay 35would not operate. Consequently, when relay 34 releases after the seconddigit series of dial pulses,

with the preselected switch, the test relay being relay 23 will beoperated in series with cut-oi! relay 15 to effect operations which havebeen previously described. In the present case, however, the closure 01contacts A and C of relay 23 will be without effect as the sequenceswitch is no longer associated with switch X, and the line circuit,instead of being extended through contact B of switching relay 28, whichis now unoperated, is extended through contact C of this relay andcontact E of key 9 to grounded negative battery.

The line circuit now extends from negative battery, contact E of key 9,contact C of relay 28, contact G of relay 23, line wiper 5, contact 13of cut-off relay 15, both windings of polar relay 14, transmitter 16,printer magnets 17, break key 18 to ground. The direction of linecurrent holds relay l4 unoperated. The central station operator thenthrows key 9 to the left, connecting the line circuit through contact Dof key 9, winding of relay 32, transmitter 40 to positive battery, thusreversing the current in the subscribers line 1. This reversal ofcurrent causes line relay 14 to close its contact and operate thecontrol relay 19. Operation of the control relay starts the subscribersprinter motor 41 and shunts the high resistance winding of line relay14. The line current is now increased to its normal working value, andas the central station printer motor is running continuously,telegraphic communication can be carried on between the two stations.

When the message has been transmitted, the central station operator candis-establish the connection by throwing the key 9 to the extreme right.This operation reconnects negative potential to the line, throughcontact E of key 9, and at contact B, removes ground from the dial lead11, thus allowing relays 12 and 24 to release. As previously explained,the release of relay 12 conditions the switch X for subsequentlyanswering a calling subscribers line. Release of relay 24, as previouslydescribed, effects the restoration of the switch and its associatedrelays, and also the release of the cut-off relay 15. The release of thecut-off relay reconnects the subscribers line 1 to negative batterythrough the winding of the line relay 2. Negative potential on thesubscribers line 1 (first through the key 9 and later through the linerelay 2) causes the line relay 14 at the subscribers station to open itscontacts and release the control relay 19. The release of this relayshuts oil the motor 41 and removes the shunt from the high resistancewinding of the line relay 14. All circuits are thus restored to normal.

What is claimed is:

1. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches having access to said lines, a line relay operablewhen a line calls, a group relay responsive to the operation of the linerelay, and a test re-,

lay, common to said switches and associated with a preselected idleswitch by the operation of the group relay, for controlling the extentof both motions of said switch.

2. The combination of a plurality of subscribers lines, a plurality oftwo-motion switcheshaving access to said lines, a test relay common tosaid switches, a preselector for selecting an idle switch, a line relayoperable when a line calls, a group relay, responsive to the operationof the line relay, for associating the test relay thereafter effectiveto control the extent or both motions of said switch.

3. The combination of a plurality of sub scribers lines, a plurality oftwo-motion switches having access to said lines, a test relay and aninterrupter common to said switches, a preselector for selecting an idleswitch, a line relay operable when a line calls, a group relay,responsive to theoperation of the line relay, for

causing the interrupter to control both motions of the preselectedswitch and the test relay to control the interrupter, whereby bothmotions of the switch are ultimately controlled by said test relay.

4. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches acting as combination line finders and connectorshaving access to said lines, a test relay common to the combinationswitches for controlling both motions of any switch when the switch isused as a line finder, and a test relay in each switch for controllingone motion of said switch when said switch is used as a connector.

5. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches having access to said lines, and a test relay commonto said switches for controlling the extent of both motions of anyswitch.

6. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches having access to said lines, a preselector forselecting an idle switch, a line relay, operable when a line calls, forpredetermining the extent of one motion of the switch, a group relay,responsive to the operation of the line relay, for predetermining theextent of the other motion of the switch, an interrupter, and a testrelay common to said switches and associated with the selected switch bythe operation of the group relay, said interrupter being effective tocause both predetermined motions of the switch, and said test relaybeing effective to disconnect the interrupter from the switch at thetermination of each motion.

7. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches, a common interrupter for said switches, and a testrelay likewise common to said switches for causing the interrupter tostart one motion of any switch after the other motion of the same switchhas been completed.

8. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches having access to said lines, a preselector forselecting an idle switch, a line relay, operable when a line calls, forpredetermining the motion of said switch in one direction, a grouprelay, responsive to the operation of the line relay, for predeterminingthe motion of said switch in the other direction, an interrupter, and atest relay both common to said switches and associated with the selectedswitch by the operation of the group relay, said interrupter beingefiective to cause both predetermined motions of said switch and saidtest relay being effective to cause said interrupter to start one motionof said switch after the other motion has been completed.

9. The combination of a plurality of subscribers lines, a plurality oftwo-motion switches having access to said lines, an interrupter commonto said switches for effecting both motions of any switch, and a testrelay likewise comlines, each switch being provided with two rotary testwipers and a single test relay, a test relay common to said switches,one of said test wipers co-operating with the test relay individual to aparticular switch when said switch is operated as a connector, and theother test wiper co-operating with the common test relay when saidswitch is used as a finder.

FREDERICK G. HALLDEN.

